Displaying Missing Name

Hi LemonKing  - Your full name fields are not matching at all between the two tables.

you can create a calculated column 

Test Match =
IF (
CONTAINS ( 'Training List',
'Training List'[Full Name],
'Staff Listing'[Full Name (by Formula)]
),
"In Training",
"Not in Training"
)

best practice should be at power query you can try below suggestions:

On both tables:

Transform → Format → Trim , Transform → Format → Clean, 

Transform → Format → Uppercase

try the below measures now to get the count 7

No Training Employees =
EXCEPT (
VALUES ( 'Staff Listing'[Full Name (by Formula)] ),
VALUES ( 'Training List'[Full Name] )
)

No Training Count =
COUNTROWS (
EXCEPT (
VALUES ( 'Staff Listing'[Full Name (by Formula)] ),
VALUES ( 'Training List'[Full Name] )
)
)

No Training Count =
COUNTROWS (
EXCEPT (
VALUES ( 'Staff Listing'[Full Name (by Formula)] ),
VALUES ( 'Training List'[Full Name] )
)
)

Hope this helps.